Method for applying a material containing a meltable polymer with blocked NCO groups

ABSTRACT

A method of applying a material comprising a fusible polymer comprises the step of:applying a filament of the at least partly molten material comprising a fusible polymer from a discharge opening of a discharge element to a first substrate.The fusible polymer has the following properties:a melting point (DSC, differential scanning calorimetry; 2nd heating at heating rate 5° C./min) within a range from ≥35° C. to ≤150° C.;a glass transition temperature (DMA, dynamic-mechanical analysis to DIN EN ISO 6721-1:2011) within a range from ≥−70° C. to ≤110° C.;wherein the filament, during the application process, has an application temperature of ≥100° C. above the melting point of the fusible polymer for ≤20 minutes.There are furthermore blocked NCO groups present in the material comprising the fusible polymer.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a national stage application under 35 U.S.C. § 371of PCT/EP2019/068799, filed Jul. 12, 2019, which claims the benefit ofEuropean Application No. 18183688.3, filed Jul. 16, 2018, each of whichis incorporated herein by reference.

FIELD

The present invention relates to a method of applying a materialcomprising a fusible polymer, comprising the step of applying a filamentof the at least partly molten material comprising a fusible polymer froma discharge opening of a discharge element to a first substrate.

BACKGROUND

Additive manufacturing methods refer to those methods by which articlesare built up layer by layer. They therefore differ markedly from otherprocesses for producing articles such as milling or drilling. In thelatter methods, an article is processed such that it takes on its finalgeometry via removal of material.

Additive manufacturing methods use different materials and processingtechniques to build up articles layer by layer. In fused depositionmodeling (FDM) methods, for example, a thermoplastic wire is liquefiedand deposited onto a movable construction platform layer by layer withthe aid of a nozzle. Solidification gives rise to a solid article. Thenozzle and construction platform are controlled on the basis of a CADdrawing of the article. An early patent document for this technology isU.S. Pat. No. 5,121,329. If the geometry of this article is complex, forexample with geometric undercuts, support materials additionally have tobe printed and removed again after completion of the article.

The thermoplastic polyurethane according to WO 2015/197515 A1 has amelting range (DSC, differential scanning calorimetry; second heatingoperation at heating rate 5 K/min) of 20 to 170° C. and a Shore Ahardness to DIN ISO 7619-1 of 50 to 95, has a melt volume rate (MVR) ata temperature T to ISO 1133 of 5 to 15 cm³/10 min and a change in MVR inthe case of an increase in this temperature T by 20° C. of less than 90cm³/10 min. The end use is the production of articles in powder-basedadditive manufacturing methods.

WO 2016/198425 A1 discloses a thermally conductive hotmelt adhesivecomposition comprising a) at least one thermally conductive filler,wherein the thermally conductive filler comprises a mixture of flakeparticles and first spherical particles in a ratio of 10:1, and whereinthe flake particles have an aspect ratio of 1.27:7. Alternatively, thethermally conductive filler contains a mixture of second sphericalparticles having an average particle size of 35 to 55 μm and thirdspherical particles having an average particle size of 2 to 15 μm in aratio of 10:1. The thermally conductive filler is selected from thegroup consisting of tin oxide, indium oxide, antimony oxide, aluminiumoxide, titanium oxide, iron oxide, magnesium oxide, zinc oxide, oxidesof rare earth metals, alkali metal and alkaline earth metal sulfates,chalk, boron nitride, alkali metal silicate, silica, iron, copper,aluminium, zinc, gold, silver, tin, alkali metal and alkaline earthmetal halides, alkali metal and alkaline earth metal phosphates, andmixtures thereof. In addition, the composition b) comprises at least one(co)polymer selected from polyamide, thermoplastic polyamides,copolyamides, butyl rubber, polybutene, poly(meth)acrylates,polystyrene, polyurethanes, thermoplastic polyurethane, polyesters,ethylene copolymers, ethylene-vinyl copolymers, SB rubber, SEBS rubber,SI rubber, SIS rubber, SBS rubber, SIB rubber, SIBS rubber, polylactide,silicones, epoxies, polyols and mixtures thereof. According to a useclaim, the material is also to be usable as filament for 3D printing.

DE 10 2012 020000 A1 relates to a multistage 3D printing method and to adevice usable for this method. This patent application states that,after the process step referred to as unpacking, the shaped articles aresent to the final consolidation step. Subsequently, the shaped articlesare sent to further subsequent processes. This process step ispreferably executed as a heat treatment step. Parts made of Croning sandthat have been produced by the process can serve as an example here.After unpacking, these are preferably embedded again into a furtherparticulate material. However, this does not have any binder coating andpreferably has good thermal conductivity. Thereafter, the parts areheat-treated in an oven above the melting temperature of the binder. Thespecific phenolic resin of the coating in one of the preferredembodiments is crosslinked and there is a significant rise in strength.In general, hotmelt adhesives are preferred for this process step offinal consolidation. Base polymers used may preferably be: PA(polyamides), PE (polyethylene), APAO (amorphous polyalphaolefins), EVAC(ethylene-vinyl acetate copolymers), TPE-E (polyester elastomers), TPE-U(polyurethane elastomers), TPE-A (copolyamide elastomers) andvinylpyrrolidone/vinyl acetate copolymers. Further customary additionsknown to those skilled in the art, such as nucleating agents, may beadded.

Reactive hotmelt adhesives have already been described in the prior art.EP 1 036 103 B1 relates, for example, to a solvent-free moisture-curingpolyurethane hotmelt adhesive composition which is solid at roomtemperature and comprises the product of the combination of thefollowing constituents:

a) 95-3% by weight of the reaction product of a first polyisocyanate anda polymer of ethylenically unsaturated monomers having a molecularweight below 60 000, wherein said polymer has active hydrogen groups;and not a copolymer of ethylene, vinyl acetate and an ethylenicallyunsaturated monomer having at least one primary hydroxyl group;

b) 5-90% by weight of at least one polyurethane prepolymer with freeisocyanate groups prepared from at least one polyol from the group ofthe polyester diols, polyester triols, polyester polyols, aromaticpolyols and mixtures thereof and at least one second polyisocyanatewhich may be the same as or different from the first polyisocyanate; and

c) 0-40% by weight of at least one additive from the group of thecatalysts, tackifiers, plasticizers, fillers, pigments, stabilizers,adhesion promoters, rheology improvers and mixtures thereof, wherein thesum of a), b) and c) is 100% by weight.

EP 1 231 232 B1 discloses a self-supporting reactive hotmelt adhesiveelement comprising a reactive one-component hotmelt adhesive which issolid at room temperature and comprises at least one isocyanate which issolid or liquid at room temperature and at least one isocyanate-reactivepolymer and/or resin which is solid at room temperature. In oneembodiment, the isocyanate used is a masked or blocked isocyanate whichespecially eliminates the blocking or masking groups under the action ofheat and/or moisture. The process described in EP 1 232 232 B1 does notdescribe use at temperatures >160° C. The examples are essentiallyundistilled isocyanate-functional low molecular weight prepolymershaving an excess of monomeric or dimeric isocyanates. Owing to theproduction method with a distinct excess of isocyanate functionality, nolinear high molecular weight polymers are formed.

WO 2018/046726 A1 relates to a method of producing an article,comprising the steps of:

I) applying a filament of an at least partly molten constructionmaterial to a carrier, such that a layer of the construction material isobtained, corresponding to a first selected cross section of thearticle;

II) applying a filament of the at least partly molten constructionmaterial to a previously applied layer of the construction material,such that a further layer of the construction material is obtained,which corresponds to a further selected cross section of the article andwhich is bonded to the layer applied beforehand;

III) repeating step II) until the article is formed;

where at least steps II) and III) are conducted within a chamber and theconstruction material includes a fusible polymer. The fusible polymerhas a melting range (DSC, differential scanning calorimetry; 2nd heatingat heating rate 5 K/min) of >20° C. to ≤100° C. and a magnitude of thecomplex viscosity 10 (determined by viscometry measurement in the meltwith a plate/plate oscillation shear viscometer at 100° C. and a shearrate of 1/s) of >10 Pas to ≤1 000 000 Pas and the temperature within thechamber is <50° C.

SUMMARY

The problem addressed by the present invention is that of at leastpartly remedying the disadvantages in the prior art. A particularproblem addressed is that of specifying a novel processing method for(latently) reactive hotmelt adhesives.

This problem is solved by a method according to claim 1. Advantageousdevelopments are specified in the subsidiary claims. They may becombined as desired, unless the opposite is apparent from the context.

DETAILED DESCRIPTION

What is proposed in accordance with the invention is a method ofapplying a material comprising a fusible polymer, comprising the stepof:

-   -   applying a filament of the at least partly molten material        comprising a fusible polymer from a discharge opening of a        discharge element to a first substrate;        wherein the fusible polymer has the following properties:    -   a melting point (DSC, differential scanning calorimetry; 2nd        heating at heating rate 5° C./min) within a range from ≥35° C.        to ≤150° C. (preferably ≥40° C. to ≤130° C., more preferably        ≥45° C. to ≤120° C.);    -   a glass transition temperature (DMA, dynamic-mechanical analysis        to DIN EN ISO 6721-1:2011) within a range from ≥−70° C. to        ≤110° C. (preferably ≥−50° C. to ≤50° C., more preferably        ≥−45° C. to ≤20° C.);        wherein the filament, during the application process, has an        application temperature of ≥100° C. (preferably ≥120° C., more        preferably ≥180° C. and very preferably ≥200° C.) above the        melting point of the fusible polymer for ≤20 minutes (preferably        ≥1 second to ≤10 minutes, more preferably ≥1 second to ≤5        minutes, further preferably ≥1 second to ≤2 minutes, especially        preferably ≥1 second to ≤30 seconds) and        wherein there are furthermore NCO groups blocked with a blocking        agent present in the material comprising the fusible polymer.

The first substrate to which the filament is applied may be a flat orcurved surface or else the last layer applied within a 3D printingmethod.

The fusible polymer, which is generally a semicrystalline polymer,without wishing to impose any restriction, can be described as a hotmeltadhesive. It has been found that, surprisingly, such hotmelts can beprocessed briefly at temperatures well above their melting temperatureand even their decomposition temperature without occurrence ofsignificant losses in their desired properties. The breakdowntemperature is understood here to mean a temperature at which apolymeric material, within a period of ≤1 hour, more than doubles itsstorage modulus G′ (DNA, dynamic-mechanical analysis to DIN EN ISO6721-1:2011 at a frequency of 1/s), or else the storage modulus G′ fallsto a value of less than half the starting value.

The discharge opening of a discharge element is preferably a nozzle.

Particularly suitable devices for the applying of the materialcomprising a fusible polymer have been found to be printheads that workby the principle of an FDM 3D printer. This typically involves conveyinga pre-extruded strand of a thermoplastic material (solid filament)through a short heating zone in order to be extruded at the end of theheating zone through a nozzle with a smaller cross-sectional area thanthe cross-sectional area of the solid filament conveyed. During theextrusion, the printhead can be moved freely in space in XYZ direction,but is typically at a constant distance above a substrate surface, thedistance from the substrate surface usually being smaller than theaverage nozzle diameter, such that the extrudate is deformed underpressure on deposition onto the substrate. The movement speed of theprinthead is typically greater than the extrusion speed of the extrudatefrom the nozzle, as a result of which it undergoes additional tensiledeformation. In FDM methods for production of additively manufacturedcomponents, movement speeds of 20-50 mm/s are typically chosen. Betterresults are typically achieved with low movement speeds.

In the method according to the invention, by contrast, it isadvantageous to establish movement speeds (application speeds) of morethan 20 mm/s, preferably >50 mm/s and most preferably >100 mm/s. Theapplication layer thickness and the application layer width arecontrollable via the ratio of discharge rate of the material from adischarge nozzle, nozzle geometry, material pressure, movement speed ofthe nozzle and distance of the nozzle from the substrate surface. If thedischarge rate from the nozzle is lower than the movement speed and thenozzle distance from the substrate is lower than the nozzle diameter,the result is coatings with an application layer thickness lower thanthe nozzle diameter. When the nozzle distance from the substrate isgreater than the nozzle diameter and the movement speed is not equal tothe discharge rate, there is no continuous and uniform layer deposition,and therefore this embodiment is not preferred.

If the viscosity of the hotmelt at the nozzle exit is too high, thedischarge rate is limited by the pressure buildup in the printhead andthe maximum conveying output. Moreover, a high pressure at the nozzlehead, owing to a high hotmelt viscosity, typically causes distinct dieswell up to and including periodically pulsating die swell at the nozzleexit.

The maximum movement speed at which there is continuous layer depositionwith a layer thickness diameter less than the nozzle diameter istherefore a good guide value for a stable process state. The movementrate is still the preferred adjustment parameter for an FDM printer fromwhich the desired discharge rate is calculated in the printing programat a given layer distance and nozzle geometry, and the materialconveying rate is established correspondingly.

Using the movement speed of a printhead with a 0.4 mm round nozzle andassuming a substrate distance of 0.2 mm, it is also possible tocalculate the residence time in the heated part of the printhead with avolume of, for example, about 200 mm³.

The method of the invention is particularly suitable for the processingof high molecular weight hotmelt adhesives that have a molecular weightM_(w) by GPC in DMF/LiBr (1%) against polystyrene standards and afteruniversal calibration by means of a viscosity detector of >30 000,preferably >50 000, more preferably >80 000, most preferably >100 000g/mol, and/or a storage modulus G′ (plate/plate oscillation viscometerto ISO 6721-10 at a frequency of 1/s) at 20° C. above the melting pointof ≥1·10⁴ Pa, preferably ≥5·10⁴ Pa, more preferably ≥1·10⁵ Pa and mostpreferably ≥5·10⁵ Pa.

Particularly suitable hotmelts for use in the method according to theinvention have the further feature of slow crystallization below themelting temperature. This enables long open times of the adhesive attemperatures below the melting temperature, as opposed to conventionalhotmelts that are preferably joined hot, i.e. at temperatures around themelting point. In a particularly preferred embodiment, in the methodaccording to the invention, hotmelts having a long open time of ≥10seconds, preferably ≥30 seconds, more preferably ≥1 min and morepreferably ≥5 min at a temperature ≤(melting point—10° C. (preferably−20° C. and more preferably −30° C.) are used. In a further particularlypreferred embodiment, these hotmelts, after rapid cooling by applicationto a substrate having a temperature of ≤30° C. and ≥10° C., directlyafter cooling to the substrate temperature, have a storage modulus G′(plate/plate oscillation viscometer to ISO 6721-10 at a frequency of1/s) of ≥1·10⁵ Pa, preferably ≥2·10⁵ Pa, more preferably ≥3·10⁵ Pa andmost preferably ≥4·10⁵ Pa and ≤5·10⁷ Pa, preferably ≤1·10⁷ Pa and morepreferably ≤5·10⁶ Pa.

The individual extrudate filaments as formed at the nozzle exit, forexample, may assume a wide variety of different shapes depending on thenozzle geometry. Preference is given to using rotationally symmetric,box-shaped or slot-shaped nozzle geometries that enable the applicationof coating strips with a coating thickness of ≥20 μm to ≤5 mm,preferably ≥50 μm to ≤2 mm, more preferably 80 μm to ≤1 mm and mostpreferably 80 μm to ≤0.5 mm.

At the application temperatures in the method according to theinvention, the previously blocked NCO groups are deblocked, such thatpostcrosslinking of the applied material inter alia is possible. In thisrespect, the material can also be referred to as reactive or latentlyreactive. The co-reactants for the NCO groups may be in free form in thematerial, for example in the form of free hydroxyl or amino groups, orelse be generated by thermal opening of functional groups obtained byaddition. The term “postcrosslinking” also includes the case that thematerial was not crosslinked prior to the application.

It is advantageous for the method according to the invention when thedistribution of the blocked isocyanate in the polymeric matrix prior tothe application to a substrate is worse/coarser than after applicationto a substrate. This is achieved in that a blocked polyisocyanate ismelted at processing temperatures of ≥120° C., preferably ≥150° C., morepreferably ≥180° C. and most preferably ≥200° C. and incorporated intothe polymer matrix, where the blocked isocyanate melts during theapplication and at least partly dissolves in the polymeric matrix or hasan average particle size after application in the polymeric matrix of<50 μm (preferably <20 μm, more preferably <10 μm and most preferably <5μm). The average particle size can be measured here by microscopy on asection image.

It is also advantageous when the blocked polyisocyanate, prior toapplication as latently reactive hotmelt adhesive, is already in theform of a heterogeneous mixture with the polymer matrix. The solidblocked polyisocyanate can be incorporated into the fusible polymer byvarious methods. A suitable method is the coprecipitation or theco-freezing-out of an aqueous blocked polyisocyanate dispersion togetherwith an aqueous hotmelt adhesive dispersion. Another method is the jointapplication and drying of an aqueous hotmelt adhesive dispersion and anaqueous blocked polyisocyanate dispersion. Another suitable method isthe mixing of powders of a micronized hotmelt adhesive/polymer matrixand a solid micronized blocked polyisocyanate. A further method is thecryogenic grinding of a hotmelt adhesive together with a solid blockedpolyisocyanate. A further method is the mixing of a solid blockedpolyisocyanate with a hotmelt adhesive in a thermoplastic mixing processby means of a co-extruder, kneader, roll or another suitable mechanicalmixing method above the melting temperature of the thermoplastic.

In a preferred embodiment, the blocked isocyanate is liquid and isincorporated in liquid form by a suitable mechanical method, for examplerolling, kneading, stirring, into the hotmelt adhesive at temperaturespreferably below the deblocking temperature of the blocked isocyanatefor a period of <8 h (preferably <6 h, more preferably <2 h and mostpreferably <1 h). The deblocking temperature shall be defined as thetemperature at which half the blocked isocyanate is degraded within aperiod of 1 h in the presence of the Zerewitinoff-active hydrogen atomspresent in the hotmelt adhesive.

In all these methods for production of a heterogeneous mixture of thepolymeric matrix and the blocked polyisocyanate, the temperature ispreferably chosen such that preliminary reaction of the blockedisocyanate with the polymeric matrix is largely prevented. “Largelyprevented” in this context means that more than 70% (preferably 80% andmore preferably 90%) of the blocked isocyanate is still in unreactedform in the heterogeneous mixture.

Prior to the application of the reactive hotmelt adhesive in the methodaccording to the invention, there is thus preferably a heterogeneousmixture of at least one solid or liquid blocked isocyanate with a solidpolymer. In the method according to the invention, this heterogeneousmixture, prior to application to a substrate, is correspondingly heatedand preferably mixed by means of at least one shear force of ≥10/s for aperiod of ≥0.5 sec. The distribution of the blocked isocyanate in thepolymeric matrix may change here toward better distribution or a greatersurface area of the interface between blocked polyisocyanate andpolymeric matrix, preferably toward a homogeneous mixture with particlesizes of the polyisocyanate within the polymeric matrix of <20 μm(preferably <10 μm, more preferably <5 μm and most preferably <1 μm).

The good distribution of the blocked polyisocyanate in the polymericmatrix after application to a substrate may lead, after a period of <14d (preferably <7 d and more preferably <3 d), to an increase in the meltviscosity of the polymeric matrix at a temperature 20° C. above themelting point thereof of at least 50% (preferably 100% and morepreferably 200%).

In the method according to the invention, the possibility of reaction ofthe NCO groups can address two aspects of the processing of hotmeltadhesives. Firstly, thermal degradation reactions in the fusible polymercan be alleviated. Such reactions may be, for example, the cleavage ofurethane or urea groups. This aspect is already manifested at relativelylow contents of available NCO groups. Secondly, the parameters of “tack”and “softening point” of hotmelt adhesives are also advantageouslyinfluenced. This aspect is manifested at comparatively high contents ofavailable NCO groups.

The postcrosslinking of the material applied can further increase themelt modulus by at least 50% and the heat resistance of a bond by atleast 10° C.

The NCO groups are introduced into the material preferably on mixing ofthe fusible polymer with a component containing the NCO groups to givethe material to be processed. The mixing is preferably conducted undershear at temperatures below the melting point of the fusible polymer.

In a preferred embodiment, the content of blocked NCO groups is within arange from ≥0.1% by weight to ≤10% by weight (titrimetric determinationto DIN EN ISO 11909), based on the total weight of the materialcontaining a fusible polymer (preferably ≥0.3% by weight to ≤7% byweight, more preferably ≥0.5% by weight to ≤5% by weight). Blocked NCOgroups are deblocked beforehand for the determination of the NCOcontent. Examples of blocking agents are acetylacetone,3,5-dimethylpyrazole, 2-butanone oxime, E-caprolactam and mixturesthereof.

In a further preferred embodiment, the fusible polymer also has at leastone of the following properties:

-   A1) a storage modulus G′ (plate/plate oscillation viscometer to ISO    6721-10 at a frequency of 1/s) at 20° C. above the melting point of    ≥1·10⁴ Pa, preferably ≥5·10⁴ Pa, more preferably ≥1·10⁵ Pa; most    preferably ≥2·10⁵ Pa;-   A2) a storage modulus G′ (plate/plate oscillation viscometer to ISO    6721-10 at a frequency of 1/s) at 10° C. below the melting point    with prior heating to a temperature of 20° C. above the melting    point and subsequent cooling at a cooling rate of 1° C./min of    ≤1·10⁷ Pa, preferably ≤5·10⁶ Pa, more preferably ≤1·10⁶ Pa;-   A3) the storage modulus G′ (plate/plate oscillation viscometer to    ISO 6721-10 at a frequency of 1/s) of the fusible polymer at the    highest application temperature attained during the application    process is a factor of ≥10 less (preferably ≥30 less, most    preferably ≥100 less) than the storage modulus G′ (plate/plate    oscillation viscometer to ISO 6721-10 at a frequency of 1/s) at a    temperature of 20° C. above the melting point of the fusible    polymer,-   A4) at least two of properties A1) to A3).

In a further preferred embodiment, the blocked NCO groups in thematerial comprising the fusible polymer are present in a separatecomponent having an average molecular weight Mn (determined by means ofgel permeation chromatography against polystyrene standards andN,N-dimethylacetamide as eluent) of ≥340 g/mol to ≤10 000 g/mol(preferably ≥400 g/mol to ≤8000 g/mol and more preferably ≥500 g/mol to≤5000 g/mol). Examples of such separate components are water-dispersiblealiphatic hydrophilized polyisocyanate crosslinkers (hardeners) that areused in industry for the formulation of water-dispersible coatings.Preferred blocking agents in the separate component are 2-butanone oxime(MEKO), 3,5-dimethylpyrazole, caprolactam or a combination of at leasttwo of these.

In a further preferred embodiment, there are furthermore free groupshaving Zerewitinoff-active hydrogen atoms present in the materialcomprising the fusible polymer. These are preferably alcohols, thiols,polyamines, urethanes and/or ureas. Together with the NCO groups, it isthen possible for crosslinking reactions to proceed in the materialapplied. Useful examples include polyester polyols, polyether polyols,polycarbonate polyols, polyacrylate polyols, polyurethanes, polythiols,polyureas or a combination of at least two of these.

In a further preferred embodiment, the blocking agent is selected suchthat deblocking of the NCO group is not followed by release of theblocking agent as a free molecule or as a part of other molecules ormolecular moieties. In this connection, reference is also made toelimination product-free blocking agents. This has the advantage thatemissions of organic compounds caused by the blocking agent can beavoided.

In a further preferred embodiment, the blocking agent is selected fromthe group consisting of organic isocyanates, lactams, glycerolcarbonate, a compound of general formula (I):

in which X is an electron-withdrawing group, R¹ and R² independentlyrepresent the radicals H, C₁-C₂₀-(cyclo)alkyl, C₆-C₂₄-aryl,C₁-C₂₀-(cyclo)alkyl ester or amide, C₆-C₂₄-aryl ester or amide, mixedaliphatic/aromatic radicals having 1 to 24 carbon atoms which may alsobe part of a 4- to 8-membered ring and n is an integer from 0 to 5 or acombination of at least two of these.

The electron-withdrawing group X may be any substituent which results inCH acidity of the α-hydrogen. These may be for example ester groups,amide groups, sulfoxide groups, sulfone groups, nitro groups,phosphonate groups, nitrile groups, isonitrile groups, polyhaloalkylgroups, halogens such as fluorine, chlorine or carbonyl groups. Nitrileand ester groups are preferred and methyl carboxylate and ethylcarboxylate groups are particularly preferred. Also suitable arecompounds of general formula (I) whose ring optionally containsheteroatoms, such as oxygen, sulfur or nitrogen atoms. It is preferablewhen the activated cyclic ketone of formula (I) has a ring size of 5(n=1) and 6 (n=2).

Preferred compounds of general formula (I) arecyclopentanone-2-carboxymethyl ester and -carboxyethyl ester,cyclopentanone-2-carbonitrile, cyclohexanone-2-carboxymethyl ester and-carboxyethyl ester or cyclopentanone-2-carbonylmethyl.Cyclopentanone-2-carboxymethyl ester and -carboxyethyl ester and alsocyclohexanone-2-carboxymethyl ester and -carboxyethyl ester areparticularly preferred. The cyclopentanone systems are industriallyreadily obtainable by a Dieckmann condensation of dimethyl adipate ordiethyl adipate. Cyclohexanone-2-carboxymethyl ester may be produced byhydrogenation of methyl salicylate.

In the case of compounds of type (I) the blocking of the NCO groups, thedeblocking and the reaction with polyols or polyamines proceed accordingto the following exemplary scheme:

The group R represents any desired radical. The β-diketone of generalformula (I) in which R¹ and R² represent H and X represents C(O)OCH₃undergoes addition via its C—H-acidic C atom onto the free NCO-group toform a further urethane group. In this way, a molecule having a blockedNCO group is obtained. The NCO group may subsequently be deblockedagain. This is achieved by opening the cyclopentanone ring, thusformally forming a carbanion and an acyl cation.

This is represented by the intermediate shown in square brackets. Apolyol Y(OH)_(n) or a polyamine Z(NH₂)_(m) (secondary amines are ofcourse also possible) where n≥2 and m≥2 undergo formal addition onto theacyl cation with their OH group or amino group, an H atom furthermigrating to the carbanion C atom. As is readily apparent, the blockingagent remains covalently bonded.

The blocking of NCO groups, deblocking thereof and the reaction of thefunctional groups obtained after the deblocking with polyols orpolyamines based on glycerol carbonate is shown by way of example in thefollowing scheme:

The group R represents any desired radical. The glycerol carbonateundergoes addition via its free OH group onto the free NCO group to forma further urethane group. The NCO group may subsequently be deblockedagain. This is achieved by opening the cyclic carbonate ring, thusformally forming an alkoxide ion and an acyl cation. This is representedby the intermediate shown in square brackets. An alcohol Y(OH)_(n) or anamine Z(NH₂)_(m) (secondary amines are of course also possible) wheren≥2 and m≥2 undergo formal addition onto the acyl cation with their OHgroup or amino group, a proton further migrating to the carbanion Catom. As is readily apparent, the blocking agent remains covalentlybonded.

In the case of lactams ε-caprolactam is preferred. The blocking anddeblocking proceeds analogously to the two schemes shown hereinabove.The N—H group of the lactam undergoes addition onto the free NCO groupto form a urea group. Opening of the lactam ring again formally givesrise to an acyl cation and a negatively charged N atom. Alcohols oramines may undergo addition onto the acyl cation and transfer thesurplus proton to the negatively charged N atom. Here too, the blockingagent remains covalently bonded.

Preference is given to the case where the blocking agent is an organicisocyanate. The NCO group to be blocked can then react with the NCOgroup of the blocking agent to form a uretdione. The reverse reactionresults in reformation of the NCO groups which react with the availablechain extenders. It is particularly preferable when the blocking agentand the compound having the NCO group to be blocked are identical.Blocking then comprises a dimerization of the relevant compound. Thisand the reaction with polyol and polyamine are shown by way of examplein the scheme which follows.

The groups R and R′ represent any desired radicals. Deblocking resultsin opening of the uretdione ring to reform two NCO groups. These maythen be reacted with alcohols or amines Alcohols Y(OH)_(n) or aminesZ(NH₂)_(m) (secondary amines are of course also possible) where n≥2 andm≥2 undergo addition onto the NCO groups to form urethane or ureagroups.

In a further preferred embodiment, the blocking agent is selected fromacetylacetone, acetoacetic acid, malonic esters, substituted orunsubstituted pyrazoles (preferably 3,5-dimethylpyrazole), alkanoneoximes (preferably 2-butanone oxime, MEKO), secondary amines (preferablyN-tert-butyl-N-benzylamine, BEBA) or a combination of at least two ofthese.

In a preferred embodiment, the blocked isocyanate is deblocked duringthe application and bonding process in the presence of (standardliterature-disclosed) catalysts or inhibitors that accelerate or retarddeblocking.

Suitable catalysts are, inter alia, nucleophilic or electrophilic bynature and are particularly suitable as (trans)urethanization catalystsand allophanatization catalysts. A typical representative is, forexample, Sn(octoate)₂ or dibutyltin dilaurate (DBTL). The catalysts andinhibitors are specifically selected for the respective blockedisocyanate.

In a further preferred embodiment, the temperature of the extrudate atthe nozzle head is ≥120° C., preferably ≥150° C. and more preferably≥200° C. and most preferably ≥250° C.

The material is preferably dried before use in the method according tothe invention and has a water content of ≤3% by weight (preferably ≤1%by weight, more preferably ≤0.5% by weight and most preferably ≤0.1% byweight).

In a further preferred embodiment, the material in the method accordingto the invention experiences a heat integral, defined as the area of thetemperature residence time above the melting temperature ofcrosslinkable material after feeding into the extruder and prior toapplication to the substrate, of ≤2000° C.·min, preferably ≤500° C.·min,preferably ≤300° C.·min and most preferably ≤100° C.·min and ≥2° C.·min,preferably ≥5° C.·min and more preferably ≥10° C.·min. The heat integralis calculated by way of example for a residence time of 5 min at 200° C.as 200° C.·5 min=1000° C.·min.

In a further preferred embodiment, on application of the material to thesubstrate by the method according to the invention, a pressure on thesubstrate of ≥0.1 bar, preferably ≥0.5 bar, more preferably ≥0.8 bar andmost preferably ≥1 bar, and ≤50 bar, preferably ≤20 bar, more preferably≤10 bar, is built up. The pressure under consideration here is the sumtotal of the pressure that arises as a result of the conveying of thehotmelt and the pressure that the discharge opening together with thedischarge element exerts on the substrate, for example by spring load orpneumatic or hydraulic backpressure.

As well as the fusible polymer, the material may comprise furtheradditives such as fillers, pigments, adhesion improvers, levellingauxiliaries, defoamers, oxidation and hydrolysis stabilizers and thelike, but also further polymers. The total content of additives in thematerial may, for example, be ≥0.5% by weight to ≤20% by weight.

The fusible polymer may, after heating to a temperature of 20° C. abovethe melting point and cooling to 20° C. at a cooling rate of 4° C./min,within a temperature interval from 25° C. to 40° C. for ≥1 minute(preferably ≥1 minute to ≤100 minutes, more preferably ≥3 minutes to ≤80minutes, even more preferably ≥5 minutes to ≤60 minutes), have a storagemodulus G′ (determined at the respective temperature with a plate/plateoscillation viscometer according to ISO 6721-10 at a frequency of 1/s)of ≥1·10⁵ Pa, preferably ≥2·10⁵ Pa, more preferably ≥3·10⁵ Pa and mostpreferably ≥4·10⁵ Pa to ≤10 MPa, preferably ≤5 MPa and more preferably≤1 MPa and, after cooling to 20° C. and storage at 20° C. for 120minutes, have a storage modulus G′ (determined at 20° C. with aplate/plate oscillation viscometer according to ISO 6721-10 at afrequency of 1/s) of ≥20 MPa (preferably ≥50, more preferably ≥100 MPa).

The fusible polymer may also have a magnitude of the complex viscosity|η*| (determined by viscometry measurement in the melt with aplate/plate oscillation viscometer according to ISO 6721-10 at 20° C.above the melting temperature and a frequency of 1/s) of ≥100 Pas to ≤5000 000 Pas. Preferably, |η*| under these measurement conditions is ≥500Pas to ≤1 000 000 Pas, more preferably ≥1000 Pas to ≤500 000 Pas.

The magnitude of the complex viscosity |η*| describes the ratio of theviscoelastic moduli G′ (storage modulus) and G″ (loss modulus) to theexcitation frequency co in a dynamic-mechanical material analysis:

${\eta^{*}} = {\sqrt{\left\lbrack {\left( \frac{G^{''}}{\omega} \right)^{2} + \left( \frac{G^{''}}{\omega} \right)^{2}} \right\rbrack} = \frac{G^{*}}{\omega}}$

Given the complex viscosities within the range specified in accordancewith the invention, it can be assumed that, in the case of prolongedstorage at room temperature, only a technically insignificant level oftackiness, if any, will occur in the fusible polymer used.

In a further preferred embodiment, the filament is applied at a rate of≥20 mm/s. This is understood to mean the relative speed of dischargeopening and substrate. The application rate is preferably ≥50 mm/s, morepreferably ≥100 mm/s.

In a further preferred embodiment, the fusible polymer has a meltviscosity (plate/plate oscillation viscometer to ISO 6271-10 at afrequency of 1/s) at a temperature of 20° C. above the melting pointT_(m) of ≥1000 Pas to ≤500 000 Pas.

In a further preferred embodiment, the fusible polymer is selected suchthat, after storage at the maximum application temperature attained fora duration of ≤1 hour (preferably ≤30 minutes, more preferably ≤5minutes, especially preferably ≤1 minute, most preferably ≤10 seconds),the storage modulus G′ (DMA, dynamic-mechanical analysis to DIN EN ISO6721-1:2011 at a frequency of 1/s) more than doubles, or else thestorage modulus G′ (DMA, dynamic-mechanical analysis to DIN EN ISO6721-1:2011 at a frequency of 1/s) falls to a value of less than halfthe starting value. The decrease in G′ is the preferred selectioncriterion. It has been found that the polymers for use with preferencein accordance with the invention show only low gel formation, if any,whenever they unavoidably thermally decompose. In that case, there is areduced risk of blockage of a discharge nozzle in spite of onset ofcrosslinking reaction with the isocyanate.

In a further preferred embodiment, prior to the application of thematerial, it is heated from a temperature of ≤40° C., preferably ≤30°C., to the maximum application temperature within ≤5 minutes (preferably≤2 minutes, more preferably ≤1 minute).

In a preferred embodiment, the material, after production and prior touse, is stored in predominantly dry form at an air humidity of ≤30% andat temperatures of ≤30° C. and used within ≤1 year, preferably ≤6 monthsand more preferably ≤3 months. Rather than or in combination with drystorage, the material can be stored in a package impermeable to airhumidity. Such packages are known from the foods sector for storage ofmoisture-sensitive foods.

In a further-preferred embodiment, the crosslinkable material accordingto the invention is stored with exclusion of light and oxygen afterproduction and prior to use. Such packages are known from the foodssector for storage of light- and oxidation-sensitive foods.

In a further preferred embodiment, the material is heated within thedischarge element to the envisaged maximal application temperature suchthat the viscosity of the material at this temperature experiences adecrease at least by a factor of 10 (preferably at least by a factor of50, further preferably at least by a factor of 100).

In a further preferred embodiment, the distance between the surface ofthe substrate and the discharge opening of the discharge element is ≤1mm. Preference is given to a distance of ≤0.5 mm, more preferably ≤0.1mm. In a further preferred embodiment of the method according to theinvention, the nozzle is contacted directly with the substrate or has anegative distance from the substrate. This embodiment is particularlyadvantageous when the substrate is flexible and can yield to the nozzleand the pressure of the extruded hotmelt. In this particular embodiment,the discharge pressure of the hotmelt from the nozzle exceeds thecompression modulus of the substrate. This embodiment is particularlyadvantageous in the coating of fabrics, scrims, foams, soft elastic andporous materials since particularly good contact can be generated here.

The discharge element with its discharge opening can be run over thefirst substrate in contact with the first substrate with a constantpressure. The pressure may be adjusted, for example, via a springelement, a hydraulic element or a pressure transducer. What isadvantageous in this method, particularly in combination with anynegative distance of the discharge nozzle from the substrate, is thatany unevenness or surface roughness on the substrate can be compensatedfor by the constant pressure mode without having to continuously changethe programming of the pressure application.

Alternatively or additionally, the distance of the nozzle from thesubstrate can be measured continuously by a continuous distancemeasurement, for example by means of laser measurement, and readjustedcontinuously.

In a further preferred embodiment, the material is applied to the firstsubstrate at a pressure of ≥0.001 bar, preferably ≥0.1 bar, morepreferably ≥0.5 bar.

Preferably, the fusible polymer is a polyurethane at least partlyobtainable from the reaction of aromatic and/or aliphaticpolyisocyanates with suitable (poly)alcohols and/or (poly)amines orblends thereof. Preferably, at least a proportion of the (poly)alcoholsused comprises those from the group consisting of: linear polyesterpolyols, polyether polyols, polycarbonate polyols, polyacrylate polyolsor a combination of at least two of these. In a preferred embodiment,these (poly)alcohols or (poly)amines bear terminal alcohol and/or aminefunctionalities. In a further preferred embodiment, the (poly)alcoholsand/or (poly)amines have a molecular weight of 52 to 10 000 g/mol.Preferably, these (poly)alcohols or (poly)amines as feedstocks have amelting point in the range from 5 to 150° C. Preferred polyisocyanatesthat can be used at least partly for preparation of the fusiblepolyurethanes are selected from the group comprising: TDI, MDI, HDI,PDI, H12MDI, IPDI, TODI, XDI, NDI, decane diisocyanate or a combinationof at least two of these. Particularly preferred polyisocyanates areHDI, PDI, H12MDI, MDI and TDI.

In a further preferred embodiment, the fusible polymer comprises apolyurethane obtainable from the reaction of a polyisocyanate componentand a polyol component, said polyol component comprising a polyesterpolyol having a no-flow point (ASTM D5985) of ≥25° C.

If appropriate, in the reaction to give the polyurethane, it is alsopossible to use diols from the molecular weight range of ≥62 to ≤600g/mol as chain extenders.

The polyisocyanate component may comprise a symmetric polyisocyanateand/or a nonsymmetric polyisocyanate. Examples of symmetricpolyisocyanates are 4,4′-MDI and HDI.

In the case of asymmetric polyisocyanates, the steric environment of oneNCO group in the molecule is different from the steric environment of afurther NCO group. One isocyanate group then reacts more quickly withisocyanate-reactive groups, for example OH groups, while the remainingisocyanate group is less reactive. One consequence of the asymmetricconstruction of the polyisocyanate is that the polyurethanes formed withthese polyisocyanates also have a less linear structure.

Examples of suitable nonsymmetric polyisocyanates are selected from thegroup consisting of: 2,2,4-trimethylhexamethylene diisocyanate,ethylethylene diisocyanate, nonsymmetric isomers of dicyclohexylmethanediisocyanate (H₁₂-MDI), nonsymmetric isomers of1,4-diisocyanatocyclohexane, nonsymmetric isomers of1,3-diisocyanatocyclohexane, nonsymmetric isomers of1,2-diisocyanatocyclohexane, nonsymmetric isomers of1,3-diisocyanatocyclopentane, nonsymmetric isomers of1,2-diisocyanatocyclopentane, nonsymmetric isomers of1,2-diisocyanatocyclobutane,1-isocyanatomethyl-3-isocyanato-1,5,5-trimethylcyclohexane (isophoronediisocyanate, IPDI), 1-methyl-2,4-diisocyanatocyclohexane,1,6-diisocyanato-2,2,4-trimethylhexane,1,6-diisocyanato-2,4,4-trimethylhexane,5-isocyanato-1-(3-isocyanatoprop-1-yl)-1,3,3-trimethylcyclohexane,-isocyanato-1-(4-isocyanatobut-1-yl)-1,3,3-trimethylcyclohexane,1-isocyanato-2-(3-isocyanatoprop-1-yl)cyclohexane,1-isocyanato-2-(2-isocyanatoeth-1-yl)cyclohexane,2-heptyl-3,4-bis(9-isocyanatononyl)-1-pentylcyclohexane, norbornanediisocyanatomethyl, 2,4′-diphenylmethane diisocyanate (MDI), 2,4- and2,6-tolylene diisocyanate (TDI), derivatives of the diisocyanateslisted, especially dimerized or trimerized types, or a combination of atleast two of these.

Preference is given to 4,4′-MDI or a mixture comprising IPDI and HDI aspolyisocyanate component.

The polyol component includes a polyester polyol having a no-flow point(ASTM D5985) of ≥25° C., preferably ≥35° C., more preferably ≥35° C. to≤55° C. To determine the no-flow point, a test vessel containing thesample is set in slow rotation (0.1 rpm). A flexibly mounted measurementhead dips into the sample and, on attainment of the no-flow point, movesaway from its position as a result of the abrupt increase in viscosity;the resulting tilting motion triggers a sensor.

Without being restricted to a theory, it is assumed that polyurethanesbased on the above-discussed nonsymmetric polyisocyanates and polyesterpolyols having the no-flow points specified have such a constructionthat the groups that originate from the polyisocyanates in the polymerconstitute soft segments, and the groups that originate from thepolyester polyols in the polymer constitute hard segments.

Examples of polyester polyols which can have such a no-flow point arereaction products of phthalic acid, phthalic anhydride or symmetricα,ω-C₄- to C₁₀-dicarboxylic acids with one or more C₂- to C₁₀-diols.They preferably have a number-average molecular weight M_(n) of ≥400g/mol to ≤6000 g/mol. Suitable diols are especially monoethylene glycol,butane-1,4-diol, hexane-1,6-diol and neopentyl glycol.

Preferred polyester polyols are specified hereinafter, stating theiracid and diol components: adipic acid+monoethylene glycol; adipicacid+monoethylene glycol+1,4-butanediol; adipic acid+1,4-butanediol;adipic acid+1,6-hexanediol+neopentyl glycol; adipic acid+1,6-hexanediol;adipic acid+1,4-butanediol+1,6-hexanediol; phthalicacid(anhydride)+monoethylene glycol+trimethylolpropane; phthalicacid(anhydride)+monoethylene glycol, polycaprolactones. Preferredpolyurethanes are obtained from a mixture comprising IPDI and HDI aspolyisocyanate component and a polyol component comprising anaforementioned preferred polyester polyol. Particularly preferred forconstructing the polyurethanes is the combination of a mixturecontaining IPDI and HDI as the polyisocyanate component with a polyesterpolyol formed from adipic acid+butane-1,4-diol+hexane-1,6-diol.

It is further preferable that the polyester polyols have an OH number(DIN 53240) of ≥25 to ≤170 mg KOH/g and/or a viscosity (75° C., DIN51550) of ≥50 to ≤5000 mPas.

One example is a polyurethane obtainable from the reaction of apolyisocyanate component and a polyol component, where thepolyisocyanate component comprises an HDI and IPDI and where the polyolcomponent comprises a polyester polyol which is obtainable from thereaction of a reaction mixture comprising adipic acid and alsohexane-1,6-diol and butane-1,4-diol with a molar ratio of these diols of≥1:4 to ≤4:1 and which has a number-average molecular weight M_(n) (GPC,against polystyrene standards) of ≥4000 g/mol to ≤6000 g/mol. Such apolyurethane may have a magnitude of the complex viscosity (determinedby viscometry measurement in the melt with a plate/plate oscillationviscometer according to ISO 6721-10 at 100° C. and a frequency of 1/s)of ≥2000 Pas to ≤500 000 Pas.

A further example of a suitable polyurethane is:

1. Substantially linear polyester polyurethanes having terminal hydroxylgroups as described in EP 0192946 A1, prepared by reaction of

a) polyester diols of molecular weight above 600 and optionally

b) diols from the molecular weight range from 62 to 600 g/mol as chainextenders with

c) aliphatic diisocyanates,

observing an equivalents ratio of hydroxyl groups of components a) andb) to isocyanate groups of component c) of 1:0.9 to 1:0.999, wherecomponent a) consists to an extent of at least 80% by weight ofpolyester diols from the molecular weight range of 4000 to 6000 based on(i) adipic acid and (ii) mixtures of 1,4-dihydroxybutane and1,6-dihydroxyhexane in a molar ratio of the diols of 4:1 to 1:4.

In the polyester polyurethanes mentioned under 1, it is preferable thatcomponent a) consists to an extent of 100% of a polyester diol of themolecular weight range from 4000 to 6000, the preparation of whichinvolved using, as diol mixture, a mixture of 1,4-dihydroxybutane and1,6-dihydroxyhexane in a molar ratio of 7:3 to 1:2.

In the polyester polyurethanes mentioned under 1, it is also preferablethat component c) comprises IPDI and also HDI.

In the polyester polyurethanes mentioned under 1, it is also preferablethat the preparation thereof involved also using, as component b),alkanediols selected from the group consisting of: 1,2-dihydroxyethane,1,3-dihydroxypropane, 1,4-dihydroxybutane, 1,5-dihydroxypentane,1,6-dihydroxyhexane or a combination of at least two of these, in anamount of up to 200 hydroxyl equivalent percent, based on component a).

In a further preferred embodiment of the method of the invention, thefusible polymer, after heating to 20° C. above its melting point andcooling to 20° C. at a cooling rate of 4° C./min, within a temperatureinterval from 25° C. to 40° C. for ≥1 minute (preferably ≥1 minute to≤100 minutes, more preferably ≥5 minutes to ≤60 minutes), has a storagemodulus G′ (determined at the respective temperature with a plate/plateoscillation viscometer according to ISO 6721-10 at a frequency of 1/s)of ≥100 kPa to ≤10 MPa and, after cooling to 20° C. and storage at 20°C. for 120 minutes, has a storage modulus G′ (determined at 20° C. witha plate/plate oscillation viscometer according to ISO 6721-10 at afrequency of 1/s) of ≥20 MPa (preferably ≥50 MPa, preferably ≥100 MPa).

In a further preferred embodiment, the material applied is contactedwith a second substrate. An adhesive bond can thus be formed. Thebonding is preferably effected under pressure until the polymer hascooled down to room temperature. The contacting is preferably effectedunder a pressure of ≥0.1 bar and ≤100 bar, preferably ≥0.5 bar and ≤20bar, more preferably ≥1 bar and ≤10 bar.

The two substrates may be the same or different.

Suitable substrates are, for example, paper, paperboard, wood, metal,ceramic, leather, synthetic leather, rubber materials, any plastics,including polyurethane-based plastics and foams thereof, and homo- orcopolymers of vinyl chloride. Polyvinyl acetate, polyethylene-vinylacetate.

In a further preferred embodiment, the second substrate includes ahotmelt adhesive and this is contacted with the material applied.Preferably, this hotmelt adhesive is the same material as already usedin the method according to the invention or at least also comprises thefusible polymer used in the method according to the invention. Thecontacting is preferably effected under a pressure of ≥0.1 bar and ≤100bar, preferably ≥0.5 bar and ≤20 bar, more preferably ≥1 bar and ≤10bar. It is alternatively preferable that the temperature of the hotmeltadhesive of the second substrate is ≤10° C., preferably ≤20° C., morepreferably ≤30° C., below the melting temperature of this adhesive. Itis further preferable that the contacting is effected at a temperatureof ≤40° C., preferably ≤30° C.

In a further preferred embodiment, the material is heated to the maximumapplication temperature within the nozzle, the material is introducedinto the nozzle at an input rate and discharged from the nozzle at anoutput rate, and the output rate is greater than the input rate. Theoutput rate may, for example, be 3 times, 4 times or up to 10 timesgreater than the input rate. The specific rate ratios depend on thediameter of a filament of the material introduced into the nozzle and onthe filament geometry of the material discharged.

In a further preferred embodiment, the at least partly molten materialis subjected to a pressure of ≥0.5 MPa within the nozzle. The pressuremay also be ≥1 MPa or ≥5 MPa.

In a further preferred embodiment, the nozzle is moved sufficientlyclose to the substrate that the material pressure in the nozzle risesabove the calculated theoretical pressure since the distance of thenozzle from the substrate is less than the average diameter of thenozzle. The pressure may also be ≥1 MPa or ≥2 MPa.

In a further preferred embodiment, the method is a method of producingan article from the material comprising a fusible polymer and the methodcomprises the steps of:

I) applying a filament of the at least partly molten material to acarrier so as to obtain a layer of the material, corresponding to afirst selected cross section of the article;

II) applying a filament of the at least partly molten material to apreviously applied layer of the material so as to obtain a further layerof the material, corresponding to a further selected cross section ofthe article and bonded to the layer applied beforehand;

III) repeating step II) until the article has been formed.

In this embodiment, an article is constructed layer by layer. Theprocess is accordingly a melt layering or fused deposition modeling(FDM) process. If the number of repetitions for the applying issufficiently low the article to be constructed may also be referred toas a two-dimensional article. Such a two-dimensional article can also becharacterized as a coating. For example, for construction thereof, ≥2 to≤20 repetitions for the application can be conducted.

An electronic model of the article to be formed is advantageously heldin a CAD program. The CAD program can then calculate cross sections ofthe model that become cross sections of the article by application ofthe filament.

Step I) relates to the construction of the first layer on a carrier.Subsequently, step II), in which further layers are applied topreviously applied layers of the material, is executed until the desiredend result in the form of the article is obtained. The at least partlymolten material (also called construction material in the terminology of3D printing) bonds to existing layers of the material in order to form astructure in z direction.

In a further preferred embodiment, the substrate is a textile, a foil, apaper, a cardboard, a foam, a mould component, part of a shoe, a circuitboard for electronic circuits, an electronics housing part or anelectronic component.

The invention further relates to a printable material comprising afusible polymer, wherein the fusible polymer comprises a polyurethanehaving free NCO groups.

The invention further provides for the use of a material according tothe invention comprising a fusible polymer for production of articles bymeans of additive manufacturing methods.

The present invention is elucidated in detail by the examples whichfollow, but without being restricted thereto.

Feedstocks:

Dispercoll® U 54, an anionic, high molecular weight polyurethanedispersion, sourced from Covestro Deutschland AG, was used as obtained.Dispercoll® U 54 is a raw material for production of thermallyactivatable adhesives.

Technical properties of Dispercoll® U 54:

Name of the property Test method Unit Value pH DIN ISO 976 6.0-9.0Viscosity at 20° C. spindle DIN 53019 mPa * s  40-600 L2/30 rpmNonvolatiles (1 g/1 h/125° C.) DIN EN ISO 3251 %  49-51 Density 20° C.DIN 51757 g/cm³ about 1.1 Minimum film formation DIN ISO 2115 ° C. about5 temperature

Bayhydur® BL 2867 was sourced from Covestro Deutschland AG and used asobtained.

Bayhydur® BL 2867 is a reactive blocked aliphatic polyisocyanate havinga solids content of 38.0±1.0% (DIN EN ISO 3251) in water and having aviscosity (23° C.) of <1500 mPas (DIN EN ISO 3219/A.3). The blockingagent used was 3,5-dimethylpyrazole. The molar mass (Mn) is about 1600g/mol.

Baybond® XL 6366 was sourced from Covestro Deutschland AG and used asobtained. Baybond® XL 6366 is a blocked aliphatic water-basedpolyisocyanate having a solids content of 44-46% (DIN EN ISO 3251) and aflow time (DIN 4 cup) of 10-30 s (AFAM 2008/10503). The blocking agentused was 2-butanone oxime. The molar mass (Mn) is about 2000 g/mol.

Baybond® XL 7270 was sourced from Covestro Deutschland AG and used asobtained. Baybond® XL 7270 is a blocked aliphatic water-basedpolyisocyanate having a solids content of 29-31% (DIN EN ISO 3251) and aviscosity (23° C.) of <100 mPas (DIN EN ISO 3219/A.3). The blockingagent used was caprolactam. The molar mass (Mn) is about 1850 g/mol.

Test Methods:

The methods detailed hereinafter for determination of the appropriateparameters were employed for conduction and evaluation of the examplesand are also the methods for determination of the parameters ofrelevance in accordance with the invention in general.

Melting point was determined by means of differential scanningcalorimetry (DSC) (Q2000, Ta Instruments) at a heating rate of 5° C./minfrom the 2nd heating.

Glass transition temperature was determined with the aid of dynamicmechanical analysis (DMA) (Q800, from TA Instruments) to DIN EN ISO6721-1:2011 at a frequency of 1 Hz. For sample preparation, a filmhaving a thickness of about 0.4 mm was pressed from the polymer filamentof thickness about 3 mm at 60° C. and a pressure of 100 bar over aperiod of 60 seconds.

The NCO groups blocked with a blocking agent are determined in the solidfusible polymer by means of gas chromatography (GC) (Agilent 6890 gaschromatograph). For this purpose, the solid fusible polymer wasdissolved in acetone at a concentration of 0.5% by weight and theninjected at an injector temperature of 290° C. On injection, theblocking agent is released at the temperature of 290° C. within theinjector and detected as a signal. The detector used was a flameionization detector (FID).

Storage modulus G′ at 20° C. above the melting point was determined bymeans of a plate/plate observation viscometer (MCR301, from Anton Paar)to ISO 6721-10 at a frequency of 1 Hz and an amplitude of 1%.

Storage modulus G′ at 10° C. below the melting point with prior heatingto a temperature of 20° C. above the melting point and subsequentcooling at 1° C./min was determined with a plate/plate observationviscometer (MCR301, from Anton Paar) to ISO 6721-10 at a frequency of 1Hz and an amplitude of 1%.

Storage modulus G′ at the highest application temperature attainedduring the application process was determined after heating to a giventemperature of 60 minutes in a plate/plate oscillation viscometer (ARES,from TA Instruments) to ISO 6721-10 at a frequency of 1 Hz and anamplitude of 1%.

Residual moisture content was determined by thermogravimetry. For thispurpose, 1 g of the filament was dried at 125° C. on a drying balance(HG 53, from Mettler Toledo) for 60 minutes and the solids content (%)was ascertained. Residual moisture content (Rf) is determined bycalculation as the difference Rf=100%−solids content (%).

INVENTIVE EXAMPLE 1

1000 g of the aqueous polyurethane dispersion Dispercoll® U 54 (50% inwater) was mixed with 65.79 g of the blocked polyisocyanate Bayhydur® BL2867 and stirred with a laboratory stirrer (from Heidolph InstrumentsGmbH & CO. KG) for 3 min. Subsequently, the mixture was immediatelystored at −12° C. for 36 hours and then at 23° C. for 24 h.Subsequently, the coarse-grain mixture present was filtered and thegrainy residue was sieved through a 4 mm sieve and dried in an aircirculation drying cabinet at 30° C. for 48 h. What was obtained was awhite coarse-grain powder having a residual moisture content of <2%.Subsequently, this was processed in a twin-screw extruder (MicroCompounder, from DSM Xplore) at 100° C. with a residence time of <5 minat 40 rpm through an orifice nozzle having a diameter of 3 mm to give astrand having a diameter of about 3 mm. The strand obtained wasprocessed in an FDM printer (X400CE, from German RepRap), modified forthe processing of 3 mm strands, with the following process conditions:construction space temperature=23° C., extrusion nozzle diameter=0.8 mm,extruder temperature=260° C., extrusion rate=70 m/s. The volume in theheating region of the nozzle is about 0.2 ml, which results in anaverage residence time of the molten material during the applicationprocess of about 6 seconds.

TABLE 1 Data of the material extruded in the twin-screw extruder Meltingpoint Tm (° C.) 45.0 Glass transition temperature Tg (° C.) −40.9Content of 3,5-dimethylpyrazole [% by wt.] 1.56 Storage modulus G′ 20°C. above Tm (Pa) 377000 Storage modulus G′ 10° C. below Tm (Pa) 720000Storage modulus G′ at 200° C. (after 60 sec) (Pa) 757 Storage modulus G′at 200° C. (after 600 sec) (Pa) 43600 Processible on the FDM printer yes

INVENTIVE EXAMPLE 2

1000 g of the aqueous polyurethane dispersion Dispercoll® U 54 (50% inwater) was mixed with 55.56 g of the blocked polyisocyanate Baybond® XL6366 and stirred with a laboratory stirrer (from Heidolph InstrumentsGmbH & CO. KG) for 3 min. Subsequently, the mixture was immediatelystored at −12° C. for 36 hours and then at 23° C. for 24 h.Subsequently, the coarse-grain mixture present was filtered and thegrainy residue was sieved through a 4 mm sieve and dried in an aircirculation drying cabinet at 30° C. for 48 h. What was obtained was awhite coarse-grain powder having a residual moisture content of <2%.Subsequently, this was processed in a twin-screw extruder (MicroCompounder, from DSM Xplore) at 100° C. with a residence time of <5 minat 40 rpm through an orifice nozzle having a diameter of 3 mm to give astrand having a diameter of about 3 mm. The strand obtained wasprocessed in an FDM printer (X400CE, from German RepRap), modified forthe processing of 3 mm strands, with the following process conditions:construction space temperature=23° C., extrusion nozzle diameter=0.84mm, extruder temperature=260° C., extrusion rate=70 m/s. The volume inthe heating region of the nozzle is about 0.2 ml, which results in anaverage residence time of the molten material during the applicationprocess of about 6 seconds.

TABLE 2 Data of the material extruded in the twin-screw extruder Meltingpoint Tm (° C.) 45.2 Glass transition temperature Tg (° C.) −41.6Content of 2-butanone oxime [% by wt.] 1.52 Storage modulus G′ 20° C.above Tm (Pa) 253000 Storage modulus G′ 10° C. below Tm (Pa) 514000Storage modulus G′ at 200° C. (after 60 sec) (Pa) 556 Storage modulus G′at 200° C. (after 600 sec) (Pa) 5610 Processible on the FDM printer yes

INVENTIVE EXAMPLE 3

1000 g of the aqueous polyurethane dispersion Dispercoll® U 54 (50% inwater) was mixed with 83.36 g of the blocked polyisocyanate Baybond® XL7270 and stirred with a laboratory stirrer (from Heidolph InstrumentsGmbH & CO. KG) for 3 min. Subsequently, the mixture was immediatelystored at −12° C. for 36 hours and then at 23° C. for 24 h.Subsequently, the coarse-grain mixture present was filtered and thegrainy residue was sieved through a 4 mm sieve and dried in an aircirculation drying cabinet at 30° C. for 48 h. What was obtained was awhite coarse-grain powder having a residual moisture content of <2%.Subsequently, this was processed in a twin-screw extruder (MicroCompounder, from DSM Xplore) at 100° C. with a residence time of <5 minat 40 rpm through an orifice nozzle having a diameter of 3 mm to give astrand having a diameter of about 3 mm. The strand obtained wasprocessed in an FDM printer (X400CE, from German RepRap), modified forthe processing of 3 mm strands, with the following process conditions:construction space temperature=23° C., extrusion nozzle diameter=0.8 mm,extruder temperature=260° C., extrusion rate=70 m/s. The volume in theheating region of the nozzle is about 0.2 ml, which results in anaverage residence time of the molten material during the applicationprocess of about 6 seconds.

TABLE 3 Data of the material extruded in the twin-screw extruder Meltingpoint Tm (° C.) 46.0 Glass transition temperature Tg (° C.) −41.6Content of ε-caprolactam [% by wt.] 2.12 Storage modulus G′ 20° C. aboveTm (Pa) 301000 Storage modulus G′ 10° C. below Tm (Pa) 568000 Storagemodulus G′ at 200° C. (after 60 sec) (Pa) 396 Storage modulus G′ at 200°C. (after 600 sec) (Pa) 21200 Processible on the FDM printer yes

NONINVENTIVE EXAMPLE 4

1000 g of the aqueous polyurethane dispersion Dispercoll® U 54 (50% inwater) was stored at −12° C. for 36 hours and then at 23° C. for 24 h.Subsequently, the coarse-grain mixture present was filtered and thegrainy residue was sieved through a 4 mm sieve and dried in an aircirculation drying cabinet at 30° C. for 48 h. What was obtained was awhite coarse-grain powder having a residual moisture content of <2%.Subsequently, this was processed in a twin-screw extruder (MicroCompounder, from DSM Xplore) at 100° C. with a residence time of <5 minat 40 rpm through an orifice nozzle having a diameter of 3 mm to give astrand having a diameter of about 3 mm. The strand obtained wasprocessed in an FDM printer (X400CE, from German RepRap), modified forthe processing of 3 mm strands, with the following process conditions:construction space temperature=23° C., extrusion nozzle diameter=0.8 mm,extruder temperature=260° C., extrusion rate=70 m/s. The volume in theheating region of the nozzle is about 0.2 ml, which results in anaverage residence time of the molten material during the applicationprocess of about 6 seconds.

TABLE 4 Data of the material extruded in the twin-screw extruder Meltingpoint Tm (° C.) 44.5 Glass transition temperature Tg (° C.) −44 Contentof blocking agent [% by wt.] 0 Storage modulus G′ 20° C. above Tm (Pa)435000 Storage modulus G′ 10° C. below Tm (Pa) 736000 Storage modulus G′at 200° C. (after 60 sec) (Pa) 781 Storage modulus G′ at 200° C. (after600 sec) (Pa) 1380 Processible on the FDM printer yes

The storage modulus at 20° C. after 600 seconds is less than twice ashigh as the storage modulus at 200° C. after 60 seconds; the example isnot in accordance with the invention.

The invention claimed is:
 1. A method of applying a material comprisinga fusible polymer, comprising: applying a filament of an at least partlymolten material comprising a fusible polymer from a discharge opening ofa discharge element to a first substrate, wherein the at least partlymolten material is applied to the first substrate at a pressure of≥0.001 bar; wherein the fusible polymer has the following properties: amelting point (DSC, differential scanning calorimetry; 2nd heating atheating rate 5° C./min) within a range from ≥35° C. to ≤150° C.; a glasstransition temperature (DMA, dynamic-mechanical analysis to DIN EN ISO6721-1:2011) within a range from ≥−70° C. to ≤110° C.; wherein thefilament, during the application process, has an application temperatureof ≥100° C. above a melting point of the fusible polymer for ≤20minutes, and wherein there are furthermore NCO groups blocked with ablocking agent present in the material comprising the fusible polymer.2. The method according to claim 1, wherein the fusible polymer also hasat least one of the following properties: A1) a storage modulus G′(plate/plate oscillation viscometer to ISO 6721-10 at a frequency of1/s) at 20° C. above the melting point of ≥1·10⁴ Pa; A2) a storagemodulus G′ (plate/plate oscillation viscometer to ISO 6721-10 at afrequency of 1/s) at 10° C. below the melting point with prior heatingto a temperature of 20° C. above the melting point and subsequentcooling at a cooling rate of 1° C./min of ≤1·10⁷ Pa; A3) the storagemodulus G′ (plate/plate oscillation viscometer to ISO 6721-10 at afrequency of 1/s) of the fusible polymer at the highest applicationtemperature attained during the application process is a factor of ≥10less than the storage modulus G′ (plate/plate oscillation viscometer toISO 6721-10 at a frequency of 1/s) at a temperature of 20° C. above themelting point of the fusible polymer; or A4) at least two of propertiesA1) to A3).
 3. The method according to claim 1, wherein the NCO groupsin the material comprising the fusible polymer are present in a separatecomponent having an average molecular weight Mn (determined by means ofgel permeation chromatography against polystyrene standards andN,N-dimethylacetamide as eluent) of ≥340 g/mol to ≤10 000 g/mol.
 4. Themethod according to claim 1, wherein there are also free groups havingZerewitinoff-active hydrogen atoms present in the material comprisingthe fusible polymer.
 5. The method according to claim 1, wherein theblocking agent is selected such that deblocking of the NCO group is notfollowed by release of the blocking agent as a free molecule or as apart of other molecules or molecular moieties.
 6. The method accordingto claim 1, wherein the blocking agent comprises acetylacetone,acetoacetic acid, malonic esters, substituted or unsubstitutedpyrazoles, alkanone oximes, secondary amines, or a combination of atleast two of these.
 7. The method according to claim 1, wherein thefilament is applied to the first substrate at a rate of ≥20 mm/s.
 8. Themethod according to claim 1, wherein the fusible polymer is selectedsuch that, after storage at the maximum application temperature attainedfor a duration of ≤1 hour, the storage modulus G′ (DMA,dynamic-mechanical analysis to DIN EN ISO 6721-1:2011 at a frequency of1/s) more than doubles or the storage modulus G′ (DMA,dynamic-mechanical analysis to DIN EN ISO 6721-1:2011 at a frequency of1/s) falls to a value of less than half the starting value.
 9. Themethod according to claim 1, wherein, prior to application of thematerial, it is heated from a temperature of ≤40° C. to a maximumapplication temperature within 5 minutes.
 10. The method according toclaim 1, wherein the discharge element with its discharge orifice is runover the first substrate in contact with the first substrate at aconstant pressure.
 11. The method according to claim 1, wherein thefusible polymer comprises a polyurethane obtained from a reaction of apolyisocyanate component and a polyol component, where the polyolcomponent includes a polyester polyol having a no-flow point (ASTMD5985) of ≥25° C.
 12. The method according to claim 1, wherein thefusible polymer, after heating to 20° C. above its melting point andcooling to 20° C. at a cooling rate of 4° C./min, within a temperatureinterval from 25° C. to 40° C. for ≥1 minute, has a storage modulus G′(determined at the respective temperature with a plate/plate oscillationviscometer to ISO 6721-10 at a frequency of 1/s) of ≥100 kPa to ≤10 MPaand, after cooling to 20° C. and storage at 20° C. for 120 minutes, hasa storage modulus G′ (determined at 20° C. with a plate/plateoscillation viscometer to ISO 6721-10 at a frequency of 1/s) of ≥20 MPa.13. The method according to claim 1, wherein the material applied iscontacted with a second substrate.
 14. The method according to claim 1,wherein the method comprises a method of producing an article from thematerial comprising a fusible polymer and the method comprises the stepsof: I) applying a filament of the at least partly molten material to acarrier so as to obtain a layer of the material, corresponding to afirst selected cross section of the article; II) applying a filament ofthe at least partly molten material to a previously applied layer of thematerial so as to obtain a further layer of the material, correspondingto a further selected cross section of the article and bonded to thelayer applied beforehand; and III) repeating step II) until the articlehas been formed.